反应等离子喷涂TiN涂层热处理后的电化学腐蚀性能

Electrochemical corrosion resistance of TiN coatings by reactive plasma spraying after heat treatment

研究了热处理后TiN涂层在模拟海水中的腐蚀行为,采用电化学阻抗谱(EIS)、动电位极化曲线、扫描电镜和能谱分析等技术研究了热处理后TiN涂层电化学腐蚀参数及组织的变化。结果表明:热处理后TiN涂层的耐蚀性明显提高,自腐蚀电流仅为热处理前的13.3%,极化电阻约是热处理前的20倍;电化学阻抗谱描绘了热处理后涂层的腐蚀过程及导致涂层腐蚀的主要因素,涂层局部的孔隙腐蚀是引起电化学腐蚀参数变化的主要因素,腐蚀初期孔隙电阻由大变小,后期又会由小变大,从而使涂层的腐蚀速率发生变化;热处理会使涂层的通孔率降低为87%,主要原因是在热处理过程,TiN与大气中的O2发生了氧化反应,生成密度较TiN小的TiO2相和Ti3O相,使涂层中的部分通孔被封闭,耐蚀性得以提高。

Corrosion behavior of TiN coatings after heat treatment in simulated seawater was studied.The change of the electrochemical corrosion parameters and the structure of TiN coating after heat treatment were investigated by electrochemical impedance spectroscopy（EIS）,potentiodynamic polarization curve,SEM and EDS analysis.The results show that the corrosion resistance of the coatings after heat treatment is increased,and its corrosion current is only 13.3% of the untreated coatings,and the polarization resistance of the heat treated TiN coatings is 20 times of that of the untreated coatings;EIS results show the corrosion process of the heat treated TiN coatings and the factors leading to the corrosion of the coatings.The local corrosion at pores in the coatings is the main factor which makes the changes of electrochemical corrosion parameters,and the pore resistance decreases in initial immersion stage and increases in late stage,which leads to the variation of corrosion rate of the TiN coatings;after heat treatment,the through porosity in the coatings decreases to 87% of the untreated coatings.It is found that during the heat treatment TiN coatings reacts with oxygen to form TiO2 and Ti3O which have lower density than TiN,therefore the partial through pores are blocked and the corrosion resistance of the TiN coatings increases.